1. Field of the Invention
This invention relates to a coordinate measuring equipment, and more particularly to coordinate measuring equipment with at least one part that is movably guided on a guideway for the measurement of a workpiece and has a drive for moving the part along the guideway.
2. Discussion of Relevant Prior Art
Such coordinate measuring equipment has been known in great variety for a long time. They are used for the three-dimensional measurement of workpieces which are to be measured, the workpiece being sensed for this purpose either mechanically or optically by a corresponding sensor. For sensing the workpiece to be measured, the sensor is then suspended on a mechanism by which it can be moved in three mutually orthogonal measuring directions. In terms of the mechanism, there are at present two current embodiments, namely, on the one hand, the so-called stand construction, and on the other hand, the so-called portal construction.
In the stand construction, the sensor is located on a horizontal extension arm. The extension arm is movably guided on a vertical stand by means of a slide, such that it can be moved both horizontally along its longitudinal axis, and also vertically along the stand. The stand is likewise, for its part, movably guided on a machine bed, and can be moved horizontally in the third measurement direction.
The structure is similar in portal measuring equipment. The sensor is here attached to a vertically aligned sleeve. The sleeve is movably guided by means of a slide on the part of the spanning portal which spans the workpiece to be measured. The sleeve can be moved by means of the slide, both vertically along its own longitudinal axis and also horizontally along the spanning portion of the portal. The portal, for its part, is likewise movably guided on a machine bed, and can be moved horizontally in the third measurement direction.
The movably guided parts, such as for example the stand, the portal, the slide, the extension arm, the sleeve, etc., are movably guided on a guideway, the corresponding movable parts being driven for movement along the guideway.
Various possibilities have long been known for the drives.
Thus it has been proposed, for example, to drive the movably guided parts by means of feed shafts operated by electric motors. Usually, a feed shaft which is stationary relative to the guideway, is parallel to the guideway, and has a thread, is rotated by an electric motor. A nut attached to the movably guided part engages with the thread of the feed shaft, and is moved along the guideway by the rotation of the feed shaft.
It has likewise been proposed to drive movably guided parts of coordinate measuring equipment by means of tie belts operated by electric motors. Here, an electric motor, which is stationary relative to the guideway, usually drives a tie belt which is firmly attached to the movably guided part, so that the movably guided part is thereby driven.
Friction wheel drives, also driven by electric motors, have also become widespread in driving coordinate measuring equipment; in them, rubber-covered friction wheels frictionally cooperate with a running surface, which is specially provided for this purpose, and thereby drive the movably guided parts. Since the movable parts are usually mounted on the guideways on highly sensitive air bearings, and the running surface is decoupled from the guideway in this case.